Oxygen is an essential element for animal life. Although deaths due to lack of oxygen occur frequently under various indoor conditions, verifying hypoxia as the cause of mortality has remained elusive. Also, the biomarkers indicating the hypoxia-induced death have not yet been clearly identified. In this study, we screened potential metabolites of which levels in animal blood can be differentiated under hypoxic conditions. Metabolites of post-mortem bloods exposed to various low-oxygen levels (3%, 5%, 8% and 12%) were compared with those from mice ambient air. GC/MS analysis showed increase in levels of lactic acid, succinic acid, uric acid and uracil in post-mortem blood from mice exposed to moderately low oxygen level (12%). Whereas samples from mice in much lower oxygen level (3% and 5%) did not show significant differences in metabolites levels. Importantly, the increase rate of these metabolites appeared to be proportional to survival time after hypoxia, suggesting that there are hypoxia-inducible cell responses including the avoidance of oxygen-dependent energetic metabolism. The results suggest that both oxygen concentration and duration exposed to hypoxia condition determine cellular metabolic pathways to increase their consequent metabolites in animal fluids, which may be used as biomarkers for tracking hypoxia.